Castor assembly

ABSTRACT

A castor assembly comprising a swivelling fork and a an upper fixing plate having, respectively, an integrally formed inner and outer bearing race, and a plastic cover providing lock-nuts for mounting and an aperture for channeling lubricant to the bearing.

The invention relates to a process for the production of shaped articlesusing splitting techniques, known per se, in particular to theproduction of concentric supporting or bearing surfaces as components ofarticles, the supporting or bearing surfaces being made by splitting theedge portions concerned of a plate-like intermediate product and thenforming them to the desired configuration of the supporting or bearingsurface without removal of metal, after which the rest of the plate isformed by flanging and/or division to a support means for the mounting,if desired so as to be movable, of the supporting or bearing surface inthe article.

Splitting techniques in which an edge portion of a plate-like article issplit and then shaped without removal of metal are, for example,disclosed in U.S. Pat. Nos. 3,540,395 and 3,758,930. The presentinvention is based on the appreciation that by appropriate adaptation ofthe rest of the plate-like intermediate product the construction ofvarious articles in which supporting or bearing surfaces are present canbe considerably simplified, both because the number of component partsof the article can be reduced, and because complicated centeringprocedures eliminated.

Thus, using the process of the invention it is possible to make arolling bearing, in particular for a castor with an upper fixing plateand a swivelling fork which carries the wheel, in which, in accordancewith the invention, the outer race of the bearing is produced bysplitting the edge of a central aperture in a plate and then calibratingto the dimensions of the rolling elements applied in the bearing, theremainder of the plate being formed by forcing to a dish with an edgeportion located in a plane surface, the said dish being closable by aflat cover having features concerning mounting and lubrication. The dishforms a space for the accommodation of a lubricating grease chamber,and, in a further embodiment of the invention, the inner bearing race isproduced by forcing the upper part of the material of the swivellingfork, so that apart from one or two covers and plugs, which may be madefrom plastics, the castor has only two elements, namely the outerbearing race with top plate and the inner bearing race produced in onepiece with the fork.

Another suitable application of the process of the invention is theproduction of the housing of an "Y-bearing", which housing has a seatingfor the outer race of the Y-bearing. In accordance with the invention,the seating is made by splitting the edge portion of an aperture in aplate, the said edge portion then being formed without removal of metalto a seating of the desired concave configuration. The bearing housingof the invention is light and strong, since at the position of themaximum bearing load the seating is fully supported by the completelyundivided plate material. In a further embodiment of the invention, theplate material may be split rather more deeply than is strictlynecessary for the formation of the bearing seating, such that during thesubsequent forming without removal of metal an annular groove is left inthe middle of the bearing seating which can function as acircumferential lubrication channel.

Embodiments of articles produced by the process according to theinvention will now be described with reference to the drawings.

FIG. 1 is a schematic representation of a castor, partly in sectionaland in side view.

FIG. 2 is a view from below the cover as applied for fixing the castorto a mobile device.

FIG. 3 is a sectional view of the housing of an Y-bearing.

FIG. 4 is a view from above the housing of the Y-bearing according toFIG. 3.

FIG. 5 is a sectional view of an improved detail of the housing as shownin FIG. 3.

According to the drawings, in particular FIGS. 1 and 2, a castor 1 ismounted in fork 2 which is mounted beneath a mobile device 5 via arolling bearing arrangement 3 and connected by screws 4. Balls 6 of therolling bearing are locked between inner and outer bearing races 7 and8. The inner race 7 is produced by rolling the tubular upper end 9 offork 2 or in general by forcing without removal of metal. An aperturewhich is closed by a plug 10, made e.g. of plastics, is located in innerrace 7 and serves for inserting balls 6 of rolling bearing 3.

The outer race 8 is made by first splitting the edge of the aperture ofa generally rectangular plate provided with a central aperture and thenforming to the desired configuration of the race. The part of the platelocated outside race 8 is then flanged so that race 8 is radially spacedapart from an edge flange 12 with holes for the passage of screws 4(shown schematically). The castor structure of FIGS. 1 and 2 iscompleted by a plastics closure 13 which is held in place by snapaction, a cover 14 and a dust-seal 15.

For a more detailed description of cover 14, which is preferably made ofplastic, e.g. nylon, reference is made to FIG. 2, according to which thecover 14, comprises four tubular projections 16 which fit into holes forthe passage of fixing screws 4 (not shown in detail). These projections16 ensure centering of the cover in relation to bearing 3 as long as thebearing is not mounted on a mobile device 5. By using e.g. nylonprojections 16, which are somewhat longer than the passage for screws 4these projections function as lock-nuts ("Nylon nuts") during mountingof the rolling bearing and guarantee safe "locking"between castor anddevice 5.

The lower side of cover 14 also comprises two concentric rims 17 and 18.Rim 18 being circumferentially continuous while rim 17 is interrupted byone or more gaps 19. Rims 17 amd 18 enclose an annular channel 20, whichwhen the cover is mounted opens on the lower side between inner andouter races 7 and 8 of the rolling bearing, so that lubricant can besupplied to balls 7 via annular channel 20 from an annular lubricantreservoir 21. This reservoir on the upper face is limited by cover 14,on the radially inner face by rim 17 and on the radially outer face bythe curved wall section connecting outer race 8 with edge flange 12.Reservoir 21 communicates with annular channel 20 via gaps 19 and can befilled by a nipple (not shown).

In the centre of cover 14 four projections 22 are formed with straightbounding surfaces 23 on their radially inner ends so that they define arectangular space. Within this space, cover 14 may be perforated for thelocation of a lock-nut by means of which the castor can be fixed in anyposition.

By choosing a suitable type of steel for the plate material in which theinner and outer races 7 and 8 are formed these races may be hardened.

FIGS. 3, 4 and 5 show the housing of a Y-bearing. Until now, suchhousings have been made of cast iron or aluminium and also of steelplate in a two or more part construction. With a casting the bearingseating must be accurately machined to give a good fit to the outer raceof the bearing. With steel plate constructions two halves, each with aspherical bearing chamber, are generally used to produce the desiredspherical bearing seating. The divided construction is less suitable forheavy loads.

According to the invention, an accurately centered and finished seatingsurface in a bearing housing may be obtained by relatively simpleoperations using splitting techniques, which is known per se. Thestarting material is a piece of steel plate 30 with a central aperture.The edge of the aperture is split and then formed without removal ofmetal to give an undivided bearing seating 31. By flanging the platematerial all round the seating 31 a flange connected to bearing seating31 by a curved portion 32 is obtained. Fixing holes 33 are made in theflanges. For mounting the outer race of a bearing in the housing, thebearing seating 31 is widened in two diametrically opposite positionsover half the width of the bearing seating to the maximum externaldiameter of the bearing to be mounted.

Such bearing housings are light and strong, since at the position of themaximum bearing load the seating ring 31 is completely supported by thecompletely undivided plate material. Seating ring 31 is accuratelycircular and the bearing is suitable for radial and axial loads. Thebearing may be mass-produced in many external forms.

A circumferential lubricating groove 35 may be readily provided inseating 31. To this end the plate material may, according to theinvention, be split somewhat more deeply than is necessary for formingseating 31 such that in the subsequent forming without removal of metalan annular groove 35 is left in the middle of the bearing seating. Theannular groove 35 then can be used as a circumferential lubricationchannel and feeded via a drill hole 36.

I claim:
 1. A castor assembly comprising an upper fixing plate ofcup-like form including a planar flange forming a top plate, an outerbearing race projecting downwardly from said flange, a swivelling forkhaving an inner race for the bearing, a plurality of rolling elements inthe annular space between the inner and outer races, a cover mounted tosaid flange overlying said races, said cover having tubular projectionswhich fit into holes for bolts in the top plate of the rolling bearing,said projections being slightly longer than the material thickness ofthe top plate at the place of the holes for the bolts such that duringmounting of the castor on a device, the projections can function aslock-nuts.
 2. A castor assembly as claimed in claim 1 wherein said outerbearing race is formed integrally with said flange and said innerbearing race is formed integrally with said swivelling fork.
 3. A castorassembly as claimed in claim 1 wherein said cover is made of a plasticmaterial.
 4. A castor assembly comprising an upper fixing plate ofcup-like form including a planar flange forming a top plate, an outerbearing race projecting downwardly from said flange, a swivelling forkhaving an inner race for the bearing, a plurality of rolling elements inthe annular space between the inner and outer races, a cover mounted tosaid flange overlying said races, concentric annular inner and outerlips projecting from the underside of the cover, said inner lip beingcircumferentially continuous and said outer lip having gaps, said lipsbeing so located that when the cover is placed on the top plate of therolling bearing, the annular space between the lips is adjacent to theball race in the bearing while the annular space communicates via thegaps in the outer annular lip with a lubricant reservoir which surroundsthe outer annular lip.
 5. A castor assembly as claimed in claim 4wherein said outer bearing race is formed integrally with said flangeand said inner bearing race is formed integrally with said swivellingfork.